November 18, 2011 9:57 pm

A raw deal for staying slim

A Harvard study shows that cooking substantially increases the energy a mammal extracts from vegetables and meat

If you want to lose weight, eat your food raw. That is the implication of a groundbreaking study by Harvard University researchers who say they are the first to study systematically the effect of cooking on the calorie content of food.

“It is astonishing that we don’t understand the fundamental properties of the food we eat,” says Rachel Carmody, the study leader. “All the effort we put into cooking food and presenting it – mashing it up, or cutting it, or slicing or pounding it – we don’t understand what effect that has on the energy we extract from food, and energy is the primary reason we eat in the first place.”

The results of the study show that for vegetables – and particularly for meat – cooking substantially increases the energy that a mammal extracts from a given portion of food. Although the experiment was carried out with mice, the scientists are confident that the same conclusions would apply to humans, another omnivorous species.

To assess the effects of different methods of food preparation, Carmody and colleagues fed groups of mice a series of diets over 40 days: meat or sweet potatoes prepared raw and whole, raw and pounded, cooked and whole, or cooked and pounded. Each animal’s body weight was tracked during the diet, as well as the amount of exercise it chose to take on a wheel.

Although pounding increased the number of calories the animals extracted from the food, cooking had a much greater effect – it broke down compounds in the raw materials into ones that are more easily digested and metabolised.

The researchers suggest that cooking may have played an important role in the evolution of our species, by increasing the energy that early humans could extract from their diet. Controlled fires and cooking date back at least 300,000 to 400,000 years – before the emergence of Homo sapiens.

“For the first time, we have a clear answer to why cooking is so important cross-culturally and biologically – because it gives us increased energy, and life is all about energy,” says Richard Wrangham, Harvard professor of biological anthropology.

The study, published in Proceedings of the National Academy of Sciences, also shows shortcomings in the calorie measurement tool used for food labelling, known as the Atwater system.

“That system is based on principles that don’t reflect the in vivo energy availability,” Carmody says. “Although it measures what has been digested, the human gastrointestinal system includes a whole host of bacteria, and those bacteria metabolise some of our food for their own benefit.”

I’ll have the steak tartare please, with some carrot sticks on the side.

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Shining a light on intelligent life

spacecraft

For many astronomers, the detection of intelligent life elsewhere in the universe would be the most exciting discovery imaginable.

Searches for alien communications through radio signals and laser pulses are the favoured methods, but the latest idea from the appropriately initialled Edwin Turner of Princeton University and his colleague Avi Loeb of the Harvard-Smithsonian Centre for Astrophysics is to look for the city lights of an extraterrestrial civilisation.

Like other methods, the technique depends on the assumption of earth-like technologies on an alien planet – in particular that the intelligent life that evolved in the light of its parent star would have artificial illumination to switch on during the hours of darkness.

The technical challenge will be to distinguish this relatively faint artificial light from the glare of the nearby star. Spotting such a small signal from a planet orbiting a distant star is beyond the capability of today’s telescopes, but Loeb and Turner say the technique could be tested and honed on the outer reaches of our solar system, among the icy bodies of the Kuiper Belt beyond Pluto.

They calculate that today’s best telescopes ought to be able to see the light generated by a Tokyo-sized metropolis out there. “It’s very unlikely that there are alien cities on the edge of our solar system, but the principle of science is to find a method to check,” Turner says. “Before Galileo, it was conventional wisdom that heavier objects fall faster than light objects, but he tested the belief and found they actually fall at the same rate.”

As human technology has moved from radio and television broadcasts to cable and fibre optics, we have become less detectable to aliens. If the same is true of extra-terrestrial civilizations, then artificial lights might be the best way to spot them from afar.

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Standing up to stem rust

Brande Wulff, stem rust researcher with goatgrass

Brande Wulff, stem rust researcher with goatgrass

A grass growing on the coastal plains of the east Mediterranean could hold the key to stopping one of the world’s most threatening cereal diseases: the Ug99 strain of stem rust fungus which is destroying wheat across Africa and moving into the Middle East and Asia.

Sharon goatgrass, whose wild populations are threatened by coastal development in Israel and Lebanon, is immune to Ug99. Scientists at the Sainsbury Laboratory and John Innes Centre in Norwich plan to isolate the genes responsible for this resistance.

Ug99, so called because it was first identified in Uganda in 1999, is a serious threat to food security because it has broken a key resistance gene that had protected commercial wheat varieties against stem rust.

When Ug99 strikes, the leaves and stems of healthy wheat grow red blister-like pustules and eventually turn into a tangle of black stems and shrivelled grains – causing huge crop losses.

“Over the next three years we aim to identify the genes that make Sharon goatgrass able to stand up to Ug99,” says Brande Wulff, the project leader. “The ultimate step, four or five years from now, is to isolate these genes … and put them into high-yielding bread wheat.”

The plan to clone several resistance genes and introduce them as a package into wheat distinguishes it from earlier one-at-a-time plant genetic engineering projects.

“This research highlights the importance of maintaining biodiversity,” says Wulff. “Wild plants can harbour powerful resistance to crop diseases.”

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The material that cleans itself

Scientists are developing a growing range of “self-cleaning” materials including glass, tiles and concrete. Dirt molecules are chemically destroyed on their surface and then washed off by wind and rain.

The latest, just launched by Alcoa, the international aluminium company, is said to be the first self-cleaning coloured cladding for buildings. EcoClean, as the coating is called, cleans not only itself but the air around it.

The key ingredient in EcoClean is titanium dioxide. In sunlight the microscopic TiO2 particles catalyse a photochemical reaction. They transfer some of their energy to water and oxygen molecules in the nearby air, forming powerful “free radicals” that oxidise and break down nearby organic compounds.

The effect is not only to clean the surface but also to destroy pollutants such as nitrogen oxides (NOx) in the surrounding air. Alcoa says that a large building covered with 1,000 sq m of EcoClean would have an air-cleansing power equivalent to 80 trees – enough to offset the smog created by four cars.

The coating itself is also made to repel water, which runs straight off the surface, carrying the broken-down dirt residues away with it.

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Late bloomers

Analysis at Ohio State University shows that over the past century Nobel laureates have become steadily older when making their prize-winning breakthroughs.

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